This invention relates to a long lasting sensor for determining the alkali and alkaline earth metal contents of molten aluminum.
During the refining of aluminum, it is necessary to reduce the sodium and lithium contents of molten aluminum to the order of a few parts per million, particularly if thin sheets are to be rolled or wire is to be extruded from the refined product.
In some Al-Si alloys, Na or Sr is added in concentrations of the order of magnitude of hundreds of ppm as a structural modifier to improve the physical properties. Since Na and Sr are very reactive metals, the efficiency of the addition is variable.
Similarly, the lithium concentration of some Al-Li alloys is in the order of several weight percent.
To produce good quality alloys, the ability to perform accurate analysis of the sodium, lithium and strontium is required.